Essential blepharospasm is a debilitating disorder of progressive involuntary spasms of the eyelid muscles (orbicularis oculi). Other muscles in the face or neck may be involved as well. Terms that sometimes are used in the description of this problem include dystonia (impaired or disordered muscle tone) and dyskinesia (a defect in voluntary movement). The onset of blepharospasm is typically in the fifth to sixth decade and is more common in women than in men.
The onset of essential blepharospasm usually is heralded by an increase in blinking or squinting with progression toward repetitive forceful closure and difficulty opening the eyelids. Blepharospasm is often made worse by stress, fatigue, bright lights, watching television or driving, and social interactions. Functional blindness in the presence of an otherwise normal visual system may result. Sleep, relaxation, walking, talking and other "tricks" may alleviate symptoms temporarily. Essential blepharospasm is a diagnosis of exclusion. The course of the disorder can fluctuate, but for most patients the disease is chronic. A thorough ophthalmic examination is necessary to diagnose essential blepharospasm because eyelid spasms frequently are secondary to ocular conditions such as blepharitis (lid inflammation), abnormal eyelashes, infections, corneal diseases, intraocular inflammation, acute glaucoma, and occasionally, cataract or macular diseases. Dry eyes, in particular, may be the cause of eyelid spasm or can aggravate coexisting essential blepharospasm. Treatment of dry eye or other ocular conditions may reduce eyelid spasm to a level that the patient can tolerate without the need for additional medications or injections.

Although the cause of essential blepharospasm is incompletely understood, it is thought to be a result of "miscommunication" in the area(s) of the brain responsible for control of the involved muscles.

Systemic medications have limited efficacy in treating the disease. However, some patients do benefit from such therapy alone or in conjunction with other treatment modalities. Local injection of a locally paralysing medication will cause relief two to three months, after which time the injections need to be repeated for continued relief.

For those patients who do not respond there are surgical options. Excision of the involved muscles can decrease blepharospasm and has been shown to be superior to procedures that remove the nerve that stimulates the spasming muscles.